1. Field of the Invention
The present invention relates to a positioning pin device and more particularly to a positioning pin device for originals or sensitive materials used in a graphic arts device such as composer for use in a photomechanical process.
2. Description of the Prior Art
A positioning pin used in a graphic arts device, which is required to be arranged accurately at a fixed position, needs to be so composed as to allow delicate adjustment about its position.
In a positioning pin device hithereto known, such as one disclosed in U.S. Pat. No. 3,860,229, a positioning pin which is radially movable is arranged in a housing, and a guide having a tapered part is arranged along the circumference of the positioning pin downward thereof such that the tapered part of the guide is pressed by means of a plurality of screws screwed in the housing, thereby adjusting radially a position of the pin in the housing.
The positioning pin device disclosed in said U.S. Pat. No. 3,860,229 not only requires an increased number of parts, but involves the following problems. That is, in the positioning pin device disclosed in said publication, since the movement of the positioning pin in the radial direction is controlled only by the guide arranged along its bottom circumference, an error several times as large as the manufacturing error between the OD of the positioning pin and the ID of the guide is produced at the top of the positioning pin where the sensitive materials, etc. to be actually subjected to the positioning are mounted, thus detracting from highly accurate positioning.
Moreover, the positioning pin device of said publication is of a construction such that the housing is installed by thrusting it into the base plate; therefore, a hole having an inner diameter equal to an outer diameter of the housing needs to be bored in the base plate. But it is difficult to bore such a hole with the correct inner diameter and perpendicular to the base plate and if the inner diameter of the hole is even a little larger than the outer diameter of the housing, the positional accuracy of the positioning pin will be affected due to such error.